The present invention relates to compressors that perform compression by rotating a rotary shaft with the power of an external drive source, and more particularly, to a sealing structure that seals about the rotary shaft to prevent fluids such as refrigerant and lubricating oil in the compressor interior, or high pressure zone, from leaking out to the compressor exterior, or low pressure zone.
Japanese Unexamined Patent Publication No. 6-300142 discloses an example of a sealing apparatus incorporated in a compressor to seal about a rotary shaft of the compressor. As shown in FIG. 7, the sealing apparatus is provided with a rubber first lip ring 91 and a second fluororesin second lip ring 2, which is arranged toward the outer side of the compressor with respect to the first lip ring 91. The first lip ring 91 and the second lip ring 92 respectively have lip portions 911, 921 that contact the outer surface 931 of a rotary shaft 93 to prevent leakage of fluid when the rotary shaft 93 is rotated or stopped.
The lip portion 911 of the first lip ring 91 permits leakage of fluid toward the second lip ring 92 during rotation of the rotary shaft 93. The fluid leaking from the lip portion 911 (mainly lubricating oil) lubricates the lip portions 911, 921 to prevent frictional deterioration and thermal deterioration caused by high temperatures. This increases the durability of the lip portions 911, 921.
It is significant that the contacting posture of the lip portion 911 with respect to the peripheral surface 931 of the rotary shaft 93 be set and maintained at an optimal state to prevent the leakage of fluid when stopping the rotation of the rotary shaft 93 while permitting leakage when rotating the rotary shaft 93, as described above. In the sealing apparatus of the above publication, the second lip ring 92 is adhered to the first lip ring 91. The contacting posture of the lip portion 911 with respect to the peripheral surface 931 of the rotary shaft 93 is maintained by the support of the second lip ring 92.
However, when the pressure in the compressor becomes high, the first lip ring 91, which is urged by the force of the high pressure, presses the lip portion 921 against the rotary shaft 93 with excessive force. This raises the temperature of the lip portion 921 and the temperature about the lip portion 921. As a result, the heated lip portion 921 affects the rubber lip portion 911, which has inferior heat resistance in comparison to fluororesin, and causes thermal deterioration.
Accordingly, it is an objective of the present invention to provide a compressor sealing structure that suppresses the deterioration of the lip portion of the first lip ring and that has superior durability.